The invention relates to the distribution of mail items whose surfaces are provided with distribution information. The distribution is effected successively with the aid of various sorting machines, particularly through successive sorting operations for the final distribution point.
In the sorting of mail items in sorting machines (e.g. letter-sorting machines, large-item-sorting machines) a separating station is normally provided for each sorting direction. If the number of mail items to be sorted exceeds the capacity of the stacker, bin or container at the separation station, the container is automatically or manually exchanged or emptied.
In certain situations, however, it can be beneficial or even necessary to flexibly adapt the sorting plan to the number of items to be sorted and the space the items occupy.
If certain sorting directions are especially heavily frequented, it is advantageous to provide numerous sorting compartments or containers for these directions, which are emptied in such a way that the sorting compartments are emptied as infrequently as possible due to the use of fullness of capacity indicators (DE 195 28 803 A1).
If a successive sorting is to be performed, a uniform loading of the sorting compartments can reduce the number of necessary sorting compartments or sorting operations. Because mail items make two or more passes through machines during successive sorting and the sequence of the re-supply of mail items into the machines must be strictly adhered to, it is particularly desirable in terms of mail item handling for the mail-item flow from any separation station not to exceed a certain amount of space. In automatic successive sorting machines, this requirement is even compulsory because the machine must store the entire volume of items internally during and between sorting passes; the space is therefore apparently limited.
To this point, the operator's experience or quantity statistics of past daily mail-item volumes has or have been used in the generation of sorting plans.
The disadvantage of this procedure is that no dynamic adaptation to the mail-item volume that is actually present is effected.
Particularly in successive sorting, solutions have become known in which a quantity statistic is created (number of mail items per distribution point) after the recording of addresses. Based on this statistic the following sorting operations can be optimized with respect to space requirements (EP 0 533 536 B1 and U.S. Pat. No. 5,363,971). Based on the quantities of items, the optimization can only be effected imprecisely because the items have different thicknesses. For a more precise assessment of the space requirements of the mail items, EP 0 661 106 A2 and EP 0 718 049 A2 proposed to detect the item thicknesses with a suitable measuring device and use this information to optimize the later sorting operations.
A more serious disadvantage is that no sorting-plan optimization is possible in the first machine pass. In automatic successive-sorting machines, this can make sorting impossible, although a suitable structuring of the first sorting plan would make sorting possible.